The present invention relates in general to sheet feeding devices for reproduction apparatus for example, and more particularly to a receiver sheet feeding device, including a vacuum corrugated duplex tray in the duplex path of a reproduction apparatus, which utilizes a combination of vacuum and air pressure to accurately acquire, separate, and feed such sheets.
In typical reproduction apparatus, such as copiers or printers for example, information is reproduced on individual cut sheets of receiver material such as plain bond paper or the like. Modem reproduction apparatus, which are capable of operating at very high speeds, have improved productivity by reproducing information on both sides of a sheet of receiver material, referred to as duplex copying. Duplex copying requires precise handling of the individual sheets of receiver material to reproduce information on the first side of each sheet, and then turn such sheet over to reproduce information on the opposite side thereof. Thus, such reproduction apparatus must include sheet feeding devices for handling receiver sheet material for rapid, reliable transport through complex travel paths within the severe environments found in the apparatus. Accordingly, the sheet feeding devices must operate to feed the receiver sheet material at the necessary high transport speeds without damage to the material, and with a minimum of stoppages due to misfeeds or multifeeds.
Devices for feeding receiver sheet material in reproduction apparatus are typically of two types, friction feeders or vacuum feeders. Friction feeders, under normal conditions, are very reliable in feeding sheets individually from a stack of sheets. However, they are particularly susceptible to misfeeds and/or multi-feeds when subject to the harsh environment found in the duplex path of reproduction apparatus. Furthermore, friction feeders have a tendency to cause undesirable marks to be left on the sheets being fed thereby. Vacuum feeders are more reliable for feeding sheets in harsh environmental conditions, but require precise complex control to assure pickup of single sheets (i.e., for prevention of misfeeds or multifeeds). Feeders relying solely on vacuum tend to be noisy, and as such are not always suitable for use in office settings.
A recent patent, U.S. Pat. No. 5,295,676, (issued Mar. 22, 1994, in the name of Kenin et al), discloses a sheet feeding device combing the aspects of friction feeders and vacuum feeders. In the feeder of this patent, the bottommost sheet in a stack of discrete sheets supported on a tray is engaged by a friction belt which serves to remove the sheet from the stack. A vacuum source adjacent to the belt increases the force of engagement of the sheet with the belt to facilitate removal from the stack. Additionally, the sheet is caused to assume a slightly corrugated shape which facilitates separation of the sheet from the remainder of the sheets in the stack on the tray. This sheet feeding device has proven relatively successful in feeding sheets of receiver material in the duplex transport path. However, it is limited in the variety of receiver material which can be reliably handled, and is still subject to misfeeds and/or multi-feeds due to the harsh environmental conditions existing in the duplex transport path.